THE PENTOSE SUGARS IN PLANT METABOLISM 



H. A. SPOEHR 

 Desert Laboratory, Tucson, Arizona 



There is no group of problems more urgent of investigation 

 and pregnant with far-reaching and practical results than those 

 dealing with the more intricate phases of plant metabolism. It 

 is high time that the realization be more generally gained that 

 all products derived from plants, be they sugar, rubber, alka- 

 loids or essential oils, are the result of metabolic activity, and 

 that the study of the mode of formation and increase of these sub- 

 stances is essentially a chemical problem. It is only by means 

 of the most thorough and painstaking investigations, and the 

 employment of the most advanced chemical technique and in- 

 terpretation that any results in this difficult field can be hoped 

 for. 



Of all the chemical substances found in plants the great 

 group of sugars commands the center of attention in considering 

 the various aspects of plant metaboHsm. All evidence points to 

 the conclusion that sugars are the first products which accumu- 

 late in the process of the photosynthetic appropriation of car- 

 bon dioxide in the chlorophyllous cell, thus forming the starting 

 point for the syntheses of the tremendous number of substances 

 found in the living organism. The manner in which sugars are 

 converted into fats and how they are incorporated into the com- 

 plex protein molecules is a problem on which as yet we have but 

 very little information. The courses of many of the other trans- 

 formations of the sugars still are explained in a purely hypotheti- 

 cal and speculative manner. But not only as synthetic mate- 

 rial are the sugars of importance in the economy of the plant, 

 but especially as sources of energy must they be regarded as 

 of greatest importance in the life of the plant. This latter 



365 



THE PLANT WORLD, VOL. 20, NO. 12 



DECEMBER, 1917 



